A tri-site rural EMS consortium (Western Massachusetts, Region VI/VII of West Virginia, and Cape Cod) coordinated by the EMS research group at Boston University Medical Center will undertake a study employing a quasi-experimental design in which the impact of three levels of EMS system development are assessed. Specifically, the study will focus on the impact of basic life support (BLS), advanced life support (ALS) implementation phase, and fully operational ALS on the process and outcome of care for cardiac patients. Process measures will be: proportions of cardiac patients using ambulances; EMT/Paramedic diagnostic and therapeutic performance; appropriate usage of "point of entry" and "referral" protocols. Outcome measures are: EMS mortality rates for cardiac patients; community-based cardiac mortality rates; excessive length of hospital stay; properties of patients admitted for the first time to a long term care facility. Secondly, we will study the determinants of rural EMS referral patterns. We will compare those patients with Killip III/IV myocardial infarctions and/or those with bradyarrhythmias requiring temporary/permanent pacing who are referred from primary to secondary hospitals with clinically comparable patients who are not referred. Thirdly, we will study the applicability of Federal EMS guidelines for system performance on a point-by-point basis using the empirical system data to assess how realistic each of the guidelines is.